The basic refrigeration cycle can be used to cool a load by having the evaporator temperature lower than the load temperature so that heat flows to the evaporator from the load. This cycle removes heat from the load which is transferred to a refrigerant flowing through the evaporator. The refrigerant leaves the evaporator as a super heated gas and flows with the compressor where additional super heat is added increasing the temperature as well as the pressure, see FIG. 1. The evaporator heat and the heat of compression are rejected from the condenser at a temperature that is higher than the evaporator temperature.
The cycle heat balance formula is: EQU Q.sub.C =Q.sub.E +Q.sub.W ( 1)
where:
Q.sub.C =condenser heat rejection PA1 Q.sub.E =evaporator heat gain PA1 Q.sub.W =heat equivalent of compressor work
The restated cycle formula in heat balance form, where 1/V.sub.R =mass flow rate is: EQU (1/V.sub.R)(h.sub.2 -h.sub.4)=(1/V.sub.R)(h.sub.1 -h.sub.4 -5)+(1/V.sub.R)(h.sub.2 -h.sub.1) (2)
Referring to FIG. 2 which shows the Pressure Enthalpy Diagram for a refrigerant cycle, the evaporator heat is equal to h.sub.1 -h.sub.5, the compression heat is equal to h.sub.2 -h.sub.1 and the condenser heat is equal to h.sub.2 -h.sub.4 ; h.sub.4 .perspectiveto.h.sub.5. The amount of work done by the compressor to produce a given refrigerant effect at the evaporator depends upon the pressure (temperature) difference between the condenser and the evaporator. The coefficient of performance (COP) for the refrigerant cycle is COP.sub.H for heating and COP.sub.C for cooling and these are defined as follows: EQU COP.sub.H =(h.sub.2 -h.sub.1)/(h.sub.2 -h.sub.1) (3) EQU COP.sub.C =(h.sub.1 -h.sub.5)/(h.sub.2 -h.sub.1) (4)
The refrigeration cycle is called a heat pump when a refrigeration cycle has a refrigerant reversing valve added so the evaporator and condenser functions are interchangeable, i.e., a load can be heated and cooled by the cycle. FIG. 3 shows a heat pump system.
Refrigeration and heat pump systems which are state of the art are as follows:
TABLE I ______________________________________ Heat Source/Sink Compressor Drive Exchanger Load Side Exchanger ______________________________________ Electric Motor Refrigerant to Air Refrigerant to Air Electric Motor Refrigerant to Fluid Refrigerant to Air Electric Motor Refrigerant to Air Refrigerant to Fluid Electric Motor Refrigerant to Fluid Refrigerant to Fluid Stirling Engine Refrigerant to Air Refrigerant to Air ______________________________________
A Stirling engine heat pump with other than a refrigerant to air heat exchangers is neither state of the art nor novel.
FIG. 4 shows a typical air to air heat pump system and FIG. 5 shows the state of the art operating characteristics for a heat pump operating in the heating mode against various heat source and heat sink temperatures.
A Stirling engine heat pump in simplistic terms is a free piston in a closed cylinder such that one end of the piston receives work from combustion while the other end of the piston imparts work to a refrigerant. FIG. 6 shows a Stirling engine heat pump operating in a heating cycle and FIG. 7 shows this system operating in a cooling cycle. Present Stirling engineer systems do not operate at efficiencies that they are capable and are therefore wasteful of energy.